1) Field of the Invention
The present invention relates to routing and, more specifically, to a tool and method for cutting and shaping materials using a router.
2) Description of Related Art
Routing is a process used to trim or cut various metal, plastic, and ceramic materials. Routers can also be used to cut composite laminated materials such as graphite. Composite laminated materials are commonly used in the airline and automotive industries due to its high strength to weight ratio, as well as its versatility to accommodate a variety of technical needs. Stiffer materials such as graphite or boron are typically embedded as fibers within a metallic or nonmetallic sheet. Alternatively, sheets of stiffer materials can be laminated to metallic or nonmetallic sheets. An example of a typical composite material is fiberglass. Because of the composite material's high strength, the router must be designed to withstand high resistance and friction when cutting. Thus, the router must be fabricated with a strong metal or carbide in order to withstand these high stresses, as well as to resist wear and dulling.
Routers are capable of cutting different shapes and patterns along an edge, trimming edges, or cutting patterns or holes in the composite material. Prior art cutters have included various features to cut composite materials, such as helical flutes having notches, grooves, or lands intended to help with improving surface finish or chip removal. The flutes may be varied in number and orientation, as well as flute geometry. Two types of routers normally used to cut composite materials are diamond plated rotary files and carbide rotary diamond point ground rasps (i.e. herringbone ground cutters).
One example of a tool used to cut composite materials is U.S. Pat. No. 4,990,035 to Scheuch et al. (“ '035 patent”). The '035 patent discloses a herringbone milling tool 1 having a clamping shank 2 and a cutting part 3, wherein there are staggered teeth extending about a helix. The staggered teeth are generally described as having a substantially pyramidal shape. The cutting part 3 defines cutting edges 5 and divider grooves 7, wherein the divider grooves extend at an opposite angle α2 to an angle α1 defining the cutting edges. “The divider grooves 7 form a secondary cutting edge 8 which, however, does not act as an actual cutting edge” (col. 4, lines 20–22). The '035 patent describes the milling cutter as capable of cutting integrated circuit boards, such as those that are reinforced with glass-fiber.
Another example of a cutting tool is U.S. Pat. No. 2,855,657 to Erhardt (“'657 patent”). The '657 patent has cutting teeth 2 arranged about a single helix. Notches 5 are disposed between the cutting teeth and serve as chip breakers. Chip breakers are not actually used to cut the workpiece, but are used to break up the chips as the cutting edges on the cutting teeth 2 are advanced through the workpiece.
Despite these features, additional innovations in cutting tooth geometry for cutting tools such as routers are desired to promote better surface finish in composite materials. Typical carbide or high-speed steels tools do not produce a desirable surface finish due to the heat generated and the abrasive nature of the graphite. Thus, the router must be able to cut and evacuate chips rapidly in order to avoid excessive heat production, which ultimately leads to poor surface finish and chattering. Chattering refers to the router flutes vibrating in a direction opposite to the direction being cut. Carbide and steel cutters dull easily, which produces excessive heat. Heat generation also leads to delamination of the material being cut. Delamination refers to separation of the layers of composite material and leads to a poor edge finish, which ultimately needs hand sanding to eliminate the delamination. Similarly, diamond coated tools do not produce an acceptable surface finish on the part, and hand sanding is usually required to clean up the parts. Also, diamond pointed tools usually have sharp points that wear out quickly and chip off easily.
It would therefore be advantageous to provide a router with an improved cutting tooth geometry that is capable of effectively cutting composite material. In addition, it would be advantageous to provide a router that produces minimal delamination and chattering. Finally, it would be advantageous to provide a router having cutting teeth that do not chip or dull easily.